This invention relates to an antenna apparatus used for a radio communication device such as a mobile telephone, in particular, to an antenna apparatus having high receiving efficiency under variable radio propagation circumstances.
Recently, with miniaturization of a mobile telephone, a space for a built-in antenna apparatus is reduced. Consequently, it becomes harder to obtain desirable antenna characteristics for the mobile telephone.
Wide directivity is (or omnidirectional characteristics are) required for the built-in antenna apparatus of the mobile telephone because movement of the mobile telephone frequently varies radio propagation circumstances. However, it is often that the built-in antenna apparatus has narrow directivity. This partially comes from influence of a casing of the mobile telephone. The narrow directivity makes receiving radio signals having different polarization planes difficult.